prolog arithmetic examples

In Prolog, is the similar to the assignment operator = in other languages. X is 1+2 means assign the result 1+2 to the variable X. The following are some arithmetic operations performed in the prolog console window.

?- X is 1+2.
 
X = 3 
 
?- X is 6-2.
 
X = 4

?- X is 2*3.
 
X = 6
 
?- X is 6/2.
 
X = 3  
 
?- X is mod(9,2).
 
X = 1